VIENNA, AUSTRIA—Aspirin improves survival in patients with tumors situated throughout the gastrointestinal (GI) tract, results from a large study in The Netherlands show. This is the first time that survival data from patients with tumors in different GI locations have been analyzed at the same time; previously, only one type of cancer, usually colorectal, was studied. The results of the study, involving nearly 14,000 patients, may lead to new insights regarding the use of aspirin in GI cancer. The study was presented at the European Cancer Congress 2015 (ECC2015).

The research team, led by the trial coordinator Martine Frouws, MD, from Leiden University Medical Centre, Leiden, The Netherlands, analyzed data from 13,715 patients a GI cancer diagnosed between 1998 and 2011. By linking the data to drug dispensing information from PHARMO, the Institute for Drug Outcomes Research based in Utrecht, The Netherlands, the team was able to show an association between aspirin use after a cancer diagnosis and overall survival (OS); they found there was a significant increase in OS among patients who did take aspirin compared with those who did not.

In total, 30.5% of patients used aspirin prediagnosis, 8.3% were solely postdiagnosis users, and 61.1% had not taken aspirin at all. The most common sites for tumors were colon (42.8% of patients), rectum (25.4%), and esophagus (10.2%). Median follow-up time for all patients was 48.6 months, with 28% of patients surviving for at least 5 years.

Patients using aspirin after their diagnosis had a chance of survival twice as high as that of those who did not use it in the same circumstances. The beneficial effect of aspirin use on survival was seen in patients with GI tumors after adjusting for potential confounding factors such as sex, age, stage of cancer, surgery, radiotherapy, chemotherapy, and other medical conditions or disorders.

"In most observational studies, an 'intention to treat' method (once an aspirin user, always an aspirin user) is used for analyzing aspirin's effect. In this study we analyzed each separate prescription per patient, and therefore we were able to achieve a more exact estimate of the effect of aspirin on cancer survival. Now we would like to analyze tumor material from these patients to try and discover which ones would benefit from aspirin treatment. Through studying the characteristics of tumors in patients where aspirin was beneficial, we should be able to identify patients who could profit from such treatment in the future," Frouws said.

The scientists believe that the beneficial effect of aspirin in cancer is due to its antiplatelet effect. Platelets are a blood component whose function is to stop bleeding by clumping and clogging blood vessel injuries. Circulating tumor cells (CTCs) are thought to hide themselves from the immune system with the help of the clothing of platelets that surround them. Aspirin inhibits platelet function and therefore allows the immune system to recognize CTCs and eliminate them.

"Medical research is focusing more and more on personalized medicine," Frouws said, "but many personalized treatments are expensive and only useful in small populations. We believe that our research shows quite the opposite: it demonstrates the considerable benefit of a cheap, well-established, and easily obtainable drug in a larger group of patients, while still targeting the treatment to a specific individual."